Hydraulic valve unit



March 15, 1955 R. s. LINDSAY I 2,704,087

HYDRAULIC VALVE AUNIT Filed Aug. s', 1 949 3 sheets-sheet 1 10M J I fMarch l5, 1955 R, s, |N|'35AY 2,704,087

HYDRAULIC VALVE UNIT Filed Aug. 5, 1949 3 sheets-sheet 2 (IttornegsMarch 15, 1955 Y R. s. LINDSAY 2,704,087

HYDRAULIC VALVE UNIT Filed Aug. 5, 1949 3 Sheets-Sheet 5 GttornegsUnited States Patent O 2,704,087 HYDRAULIC VALVE UNIT Rolland S.Lindsay, Detroit, Mich., assignor to Haller Machine and ManufacturingCompany, Detroit, Mich., a corporation of Michigan Application August 3,1949, Serial N o. 108,327 6 Claims. (Cl. 137-119) This invention relatesto hydraulic machinery and, in particular, to hydraulic control valves.

One object of this invention is to provide a hydraulic control valveunit which automatically defers the feeding of pressure fluid to a mainhydraulic device, such as a main hydraulic cylinder until anotherhydraulic device, such as an auxiliary hydraulic cylinder, has beensulficiently supplied therewith to accomplish an operation which it isdesired to accomplish prior to the start of operation of the maindevice.

Another object is to provide a hydraulic control valve unit of theforegoing character which defers this feeding of pressure fluid to themain cylinder until a predetermined pressure has been built up in theauxiliary cylinder.

Another object is to provide a hydraulic control valve unit or packagevalve which in a single assembly provides the functions of preliminarilysupplying pressure fluid to an auxiliary cylinder while a portion of thepressure fluid is permitted to flow through a constricted orifice intoanother portion of the valve, which restricted ow eventually becomessuflicient to shift another portion of the valve unit and thereafter todivert the llow of pressure iluid to the main cylinder while theauxiliary cylinder continues to remain under pressure until the maincylinder has performed its work.

Another object is to provide a hydraulic control valve unit or packagevalve of the foregoing character which is especially well adapted tosupplying pressure uid initially to a work gripping cylinder until thework, such as a metal sheet or strip, has been gripped with apredetermined pressure to hold it fast Without slipping, whereupon thevalve shifts automatically to thereafter supply pressure lluid to a mainhydraulic cylinder which then feeds the work to a work processingmachine, such as a punch press.

In the drawings:

Figure 1 is a central vertical longitudinal section through a valve unitaccording to one form of the invention, with its parts in its forwardstroke position for the start of feeding pressure fluid to an auxiliarycylinder prior to feeding it to a main cylinder;

Figure 2 is a horizontal section taken along the line 2 2 in Figure 1;

Figure 3 is a horizontal section taken along the line 3-3 in Figure l;

Figure 4 is a vertical cross-section taken along the broken line 4 4 inFigure 1;

Figure 5 is a vertical cross-section taken along the broken line 5 5 inFigure 1;

Figure 6 is a vertical longitudinal section similar to Figure 1 butshowing the valve with its parts in its return stroke position; and

Figure 7 is a diagrammatic side elevation, partly in vertical section,showing the valve unit of the invention applied to the feeding of sheetmetal to a punch press.

In general, the valve unit or package valve of this invention consistsof a valve block or casing having a central bore with a piston or spoolvalve therein, the spaced heads of which may be shifted to selectivelycontrol the distribution of pressure fluid to one of a pair of serviceports while permitting the discharge of fluid from the other serviceport through the valve to a reservoir or other point of disposal. Priorto the admission of pressure fluid to the service port, which istemporarily blocked by a pressure-responsive springpressed plunger,pressure fluid is admitted freely to an auxiliary service port leadingto an auxiliary hydraulic device, such as a work-gripping cylinder,which it is desired to actuate before a main hydraulic device, such as awork feeding cylinder, is permitted to operate. At the same time,pressure-fluid is also admitted freely "ice through a constrictedorifice leading to the operating chamber of the service port blockingpiston, building up pressure therein until this is suflcient to shiftthis valve piston and open up the main service port to the free ilow ofpressure fluid to the main cylinder. With the work thus securely held bythe auxiliary gripping cylinder, the main cylinder or feeding cylinderthen accomplishes this function of feeding the work to the machine whichit serves, such as a punch press.

When the machine has accomplished its operation upon the work, the valvespool or main valve plunger is shifted, either automatically by themotion of a portion of the machine, such as the punch press platen, ormanually. When this occurs, the heads of the valve spool or plunger havenow been shifted into positions where pressure iluid is now supplied tothe service port which was formerly in exhaust, and the service portformerly supplied with pressure fluid is now in exhaust. Before freeexhaust is permitted, however, the service port blocking piston mustagain be shifted by the building up of pressure therein as before, butthrough a different passageway on the opposite side of the blockingpiston, shifting the blocking piston and permitting free exhaust of thefluid from the service port now in exhaust. The work-gripping cylinderor auxiliary cylinder is meanwhile permitted to discharge its uid freelyinto the exhaust line, thereby releasing its grip upon the work, afterwhich the shifting of the service port blocking plunger permits thefeeding cylinder or main cylinder' to reverse its stroke and retract thework gripping device preparatory to a new feeding stroke of the maincylinder, completing the cycle.

Referring to the drawings in detail, Figures 1 to 4 inclusive show thevalve unit, generally designated 10, according to one form of theinvention, as consisting generally of a casing 11 having a cylindricalmain bore 12 closed at its opposite ends by end members or caps 13 and14 and containing a ported valve sleeve 15 in which a main valve spoolor piston valve member 16 is reciprocable. Also included in the valveunit 10, as described more in detail below, is a service port blockingvalve 17 and a pressure fluid inlet relief valve 18 having an end memberor cap 19. The casing 11 is roughly in the form of a block having on itsunder side an inlet passage or port 20 into which is threaded a pressurefluid inlet pipe 21. The inlet passage or port 20 opens into the centralportion of the main valve bore 12 and has a relief valve bore 22 openinginto it. The relief valve bore 22 has a port 23 with a conical seatsurrounding its junction with the inlet passage 20 (Figure l) and at itsouter end is closed by the cap 19 previously mentioned. Reciprocablymounted in the bore 22 is a cupshaped hollow relief valve plunger 24having its forward end beveled to engage the valve seat 23 and having areduced diameter portion 25 adjacent its forward end and containingcross ports or drainage ports 26 opening into its interior bore orsocket 27. Seated in the bore 27 is one end of a compression coil spring28, the forward end of which is seated in a corresponding socket 29within the cap 19 (Figures l and 3) and which is engaged by an abutmentdisc 30 which in turn is engaged by an adjustment screw 31 threaded intothe threaded bore 32 and having a lock nut 33 for locking it in position. The adjusting screw 32 furnishes a means of regulating thepressure exerted by the spring 28 uponthe,

relief valve plunger 24 and consequently regulates the pressure at whichthe relief valve will admit pressure fluid from the inlet passage 20into the relief valve bore 22. The cap 19 is secured tothe casing 11 byscrews 34 (Figure 3).

Opening out of the relief valve bore 22 is a reliefinto the main bore 12between the outlet passage 40 4and the pressure uid inlet passage 20 isan auxiliary service port 41 (Figures 2 and 4) into which is threaded anauxiliary service pipe 42.

The valve sleeve 15 is in the form of a hollow cylinder which is fixedin position within the main valve bore 12 and has three annular groovesin the periphery thereof, namely a middle groove 43 and end grooves 44and 45 (Figures l and 2). The middle groove 43 is aligned with thepressure fluid inlet passage 20 and has four ports 46 (Figure 4) whereassimilar ports 47 and 48 respectively open from the end grooves 44 and 45into the valve bore 49 within the valve sleeve 15 within which the valvespool or piston valve member 16 reciprocates. Due to the irregularsection line 4-4 of Figure l along which Figure 4 is taken, the upperport in the valve sleeve 15 is the port 48 in the annular groove 45,whereas the lower port is the port 46 in the annular groove 43.

Opening out of the valve bore 12 in alignment with the end grooves 44and 45 in the valve sleeve 15 are main service ports or passageways 50and 51 respectively and having main service pipes 52 and 53 threadedtherein (Figure 1). The pipes 52 and 53 lead to the opposite ends of themain hydraulic cylinder or other main hydraulic device to be controlled,whereas the auxiliary service pipe 42 (Figures 2 and 4) leads to theauxiliary hydraulic cylinder or device to be controlled, as describedbelow in connection with Figure 7. The service port blocking valve 17reciprocates to and fro transversely across the service port orpassageway 51, opening it or closing it, under the conditions describedbelow.

Reciprocably mounted within the valve sleeve bore 49 are the spacedheads 54 and 55 of the valve spool or piston valve member 16, the heads54 and 55 being spaced apart from one another bv a distance equal to theseparation of the ports 47 and 48 (Figures l and 2). The heads 54 and 55are separated from one another by the valve stem 56 of reduced diameterwhich forms, in effect, an annular chamber 57 surrounding the stem 56between the heads 54 and 55 within the valve sleeve bore 49. Beyond andto the left of the head 55, the valve member 16 is provided with a valvestem extension 58 which is surrounded by a compression spring 59, oneend of which engages the outer surface of the head 55 and the other endof which is seated against an abutment disc 60 located in the end of asocket 61 within the end cap 14, the socket 61 consisting of a boreterminating in a counterbore 62 (Figures 1 and 2). The compressionspring 59 tends to urge the valve member 16 to the right into theposition shown in Figure 6. and the abutment disc 60 also serves as astop for the end 63 of the valve stem extension 58 when the valve member16 is in its Figure l position. The end cap 14 is secured bv the screws64 to the left-hand end of the casing 11. closing that end of the valvebore 12.

To the right of the right-hand valve head 54, the valve stem 56terminates in a valve rod 65 of reduced diameter which passes through abore 66 in the end cap 13, which contains an oil ring 67 to preventleakage along the rod 65. The end can 13 is secured by the screws 68 tothe righthand end of the valve casing 11 (Figure 2). The service portblocking valve 17, which opens or closes the service port or passa ge51. consists of a hollow plunger 69 reciprocable in a bore 70 whichcrosses the service port or passage 51 transversely (Figure 4). Theplunger 69 is of a length slightlv greater than the diameter of theservice port or passage 51 so as to completely close it ofil in theposition shown in Figure 4. rhe passage 70 is long enough and hence thelcasing 11 thick enough to permit the piston plunger 69 to withdrawsubstantially completelv into the left-hand end thereof so as tocompletely open the service port or passage 51, which is shown closed inits Figure 4 position.

The closed end of the piston or plunger 69 is provided with a stopproiection 71, the end 72 of which contacts the inner surface. of aclosure plate 73 which is secured by the screws 74 (Figure 4) to thevalve casing 11 to close the right-hand end of the transverse bore 70. Aconstricted lower bv-pass port or passageway 75 of restricted diameterleads from the lower end of the service port or passageway 51 beneaththe plunger 69 to the operating chamber 76 of the plunger 69 forming theright-hand end of the transverse bore 70. The passageway 75 is of asufficiently small diameter to appreciably retard the ow of pressure uidtherethrough and hence to delay the opening of the blocking valve 17.Extending between the upper portion of the service port or passage 51above the plunger 69 and the operating chamber 76 is an L-shapedconstricted upper by-pass port or passage 77 having a valve seat 78closed by a ball check valve 79 which is urged into its closed positionby a compression spring 80, the rearward end of which is seated againsta plug 81 threaded into the counterbore 82 which joins the by-pass portor passageway 77.

The blocking valve plunger 69 is provided with a socket 83 whichreceives the forward end of a compression spring 84 (Figure 4), therearward end of which engages an abutment disc 85 mounted in theleft-hand end of the transverse bore 70. The abutment disc 85 is engagedby an adjusting screw 86 threaded through a threaded bore 87 extendingthrough a closure plate 88 which is secured by the screws 89 to thecasing 11 at the left-hand end of the valve bore 70 in a positioncomplementary to the closure plate 73. A lock nut 90 holds the screw 86in its adjusted position, the screw 86 being used to adjust the closingpressure exerted upon the valve plunger 69 and hence to regulate theopening pressure of the service port blocking valve 17.

Figure 7 shows a typical application of the valve unit 10 to delay thesupplying of pressure uid to a main hydraulic device or cylinder untilan auxiliary hydraulic device or cylinder has been actuated. Inparticular, the installation shown by way of example in Figure 7consists of a punch press, generally designated 91 having a platen orram 92 reciprocable vertically in guides 93 and having a punch 94secured to its lower end. The punch 94 cooperates with a die 95 boltedto the bed 96 of the punch press 91. Bolted to one of the guides 93 is abracket 94a to the lower end of which the valve unit 10 is bolted.Bolted to the platen 92 is a cam 97 having a curved cam surface 98 uponwhich rides a cam roller 99. The cam roller 99 is mounted upon an axle100 carried by a yoke 101 mounted on the outer end of the valve rod 65.The exhaust pipe 38 leads to an oil reservoir (not shown) whereas thepressure fluid inlet pipe 21 leads to the valve unit 10 from a hydraulicpump (also not shown). A Hexible hose 102 leads from the auxiliaryservice pipe 42 to an auxiliary hydraulic device or work clamping device103. The latter is of the type described and claimed in the Hallerapplication, Serial No. 44,622, led August 17, 1948, for Pressure FluidClamp, which is a division of Haller Patent 2,467,740, issued April 19,1949, for Step-by-Step Feeding Device, and its details are beyond thescope of the present invention.

For the purposes of the present disclosure, the clamping device 103consists of a casing or cylinder block 104 mounted bridge-like above andspanning the stock S and having its ends extending downward to rest upona movable support or cross-head 105 and separated from it by anelongated opening 106 through which the stock S passes. The stock S maybe in the form of coil stock, that is, sheet steel or other metal orsheet material in the form of a coil o1' elongated strip, and this isguided over a stationary support 107 to a position between the punch 94and a die 95. Normally, the stationary support 107 is provided with ahydraulic clamping device similar to the clamping device 103 andoperating alternately therewith from an auxiliary service port similarto the port 41 but aligned with the valve sleeve groove 44 rather thanthe groove 45 (Figure 2). The fixed clamping device releases the sheetor stock S while the movable clamping device 103 grips it and viceversa. The clamping device 103 has a coupling 108 connected to the hose102 and opening into an inclined passage 109 which leads to a pluralityof operating chambers 110 for cylinder bores 111 containing spacedparallel inclined plungers 112 engaging a transverse clamping roller 113mounted in a cavity 114 of wedge-shaped cross-section. Conseuuently,when the hose 102 and auxiliary service pipe 42 supply pressure uid tothe operating chambers 110, the plungers 112 are pushed downward in aninclined path to wedge the roller 113 into the space between thewedge-shaped cavity 114 and the upper surface of the stock S so as toclamp it firmly against the cross-head 105.

The cross-head 105 reciprocates in spaced guides 115 which are bolted asat 116 to the punch press bed 96. The guides are longitudinally groovedto guide the cross-head 105 in its reciprocation. Secured as at 117 tothe cross-head 105 is a piston rod 118 forming a part of a mainhydraulic motor 119 and connected to a stock feeding piston 120reciprocable in the bore 121 of a main hydraulic cylinder 122. Thelatter is closed at its opposite ends by heads 123 and 124 and isprovided at its opposite ends with ports 125 and 126 connectedrespectively to the service pipes 52 and 53 leading to the service portsor passages 50 and 51 respectively. Mounted on the cylinder 122 is atransverse support 127 having a guide groove 128 therein for thereception of the axle support 129 of axles 130 carrying grooved guiderollers or pulleys 131. The latter engage the opposite edges of thestock S and hold it in alignment with the opening 106 between theclamping device 103 and the cross-head 105.

Operation In the operation of the invention, such as in the punch presswork feeding installation shown in Figure 7, pressure fluid enters theuid inlet port or passage 20 through the inlet pipe 21 from the pump(not shown). When the platen 92 is in its raised position at thebeginning of its downward or working stroke, the cam roller 100 isriding on the raised portion of the cam surface 98 of the cam 97,consequently, the valve rod 65 and valve spool or valve member 16 arepushed inwardly into the position shown in Figures 1 to 5 inclusive.Consequently, pressure iluid passes through the inlet port or passage 20(Figure 1) into the middle groove 43 of the valve sleeve 15 and thencethrough the ports 46, annular chamber 57, ports 48, and left end annulargroove 45 of the valve sleeve 15 into the service port or passageway 51.This, for the time being, is blocked by the blocking valve 17 (Figure4), the piston 69 of which is yieldingly held squarely across theservice port or passage 51 by the thrust of the coil spring 84,temporarily preventing ow of pressure uid to the stock feeding piston120. Pressure uid, however, immediately flows through the constrictedlower by-pass passage 75 into the operating chamber 76 of the blockingvalve 17 at a retarded rate of speed, gradually building up pressurewithin the operating chamber 76. In the meantime, however, pressure uidhas been flowing freely out of the left end annular groove 45 in thevalve sleeve 15 through the auxiliary service port 41 (Figures 2 and 4)into the auxiliary service pipe 42 and thence through the hose 102(Figure 7) to the movable clamping device 103, shifting the plungers 112downward in an inclined path and wedging the clamping roller 113 tightlyagainst the stock S and consequently clamping the work against thecross-head 105.

In the meantime, suicient pressure uid has flowed through theconstricted lower by-pass port 75 (Figure 4) into the operating chamber76 of the blocking valve 17 to overcome the thrust of the coil spring84. As a consequence, the pressure iluid in the operating chamber 76shifts the blocking valve plunger 69 to the left, opening the connectionbetween the lower and upper portions of the service port or passage 51,thereafter permitting pressure uid to enter and flow through the servicepipe 53. The pressure fluid thus enters the rearward or right hand endof the cylinder bore 121 through the port 126 (Figure 7) and actsagainst the piston 120, causing it, the piston rod 118 and thecross-head 105 to move to the left, advancing the sheet S which has justbeen clamped thereto by the action of the pressure fluid reaching theclamping device 103 through the hose 102. It will be understood that thestationary clamping device (not shown) similar to the movable clampingdevice 103 and mounted above the stationary support 107 is unclamped atthis time while the clamping device 103 is clamped, so that the stock Sis free to be moved to the left beneath the punch 94 and over the die95.

The platen 92 now moves downward to punch the workpiece out of the stockS, and at the same time the cam 97 moves downward, causing the roller100 to ride to the low portion of the cam surface 98, permitting thevalve rod 65 and valve spool or valve member 16 to move outward (to theleft in Figure 7 or to the right in Figures 1 and 2) under the inuenceof the compression spring 59, shifting the valve spool 16 into theposition shown in Figure 6. When this occurs, the auxiliary service port41 and auxiliary service pipe 42 are immediately connected through theannular groove 45 and sleeve ports 48 to the left-hand end of the valvebore 12 (Figure 6). Consequently, lluid is immediately released from theoperating chambers 110 of the movable clamping devices 103 to ow throughthe hose 102, auxiliary service pipe 42, ports 41 and 48, left-hand endof the cylinder bore 12 into the outlet port or passage 40 and thenceinto the 6 exhaust` passage 36 and exhaust pipe 38. This releases theclamping plungers 112 and the clamping roller 113, consequentlyreleasing the clamping grip of the latter upon the stock S.

Meanwhile, the same shifting of the valve member 16 with its heads 54and 55 into the position of Figure 6 permits pressure iluid to flow fromthe inlet pipe 21 and port 20 through the middle annular groove 43 andports 46, the annular chamber 57, the right-hand end ports 47, theright-hand end groove 44, and the service port or passage 50 into theservice pipe 52 leading to the port 125 at the forward end of thecylinder 122. The pressure acts against the piston to return the crosshead 105 to its retracted position shown in Figure 7, but before it cando so, the iluid is temporarily prevented from leaving the rearward orright-hand end of the cylinder bore 121 by the blocking valve 17 whichhas closed immediately under the inuence of the coil spring 84 when thevalve was shifted to the position of Figure 6. This occurred by reasonof the connection of the operating.

of the service port 51, the ports 48, and the left-hand end of the mainvalve bore 12.

While the movable clamping device 103 has been releasing its grip, thesimilar stationary clamping device (not shown) mounted above thestationary support 107 has been gripping the stock S, it having beenconnected to an auxiliary service port similar to the port 41 (Figure2), but located near the other end of the cylinder bore in communicationwith the right-hand end groove 44. The delay which permits this to takeplace occurs by reason of the fact that the iluid being forced out ofthe right-hand end of the cylinder bore 121 through the port 126 andpipe 53, although blocked by the blocking valve 17 temporarily, passesthrough the constricted upper bypass port or passage 77, forcing thecheck valve 79 to open by overcoming the thrust of the coil spring 80.This permits pressure to build up gradually again in the operatingchamber 76 until there has been a sufficient accumulation of pressure toagain shift the blocking valve piston 69 to the left (Figure 4),reopening the service port or passage 51. The uid may then pass freelyout of the rearward end of the cylinder 122 to the exhaust pipe 38 byway of the service pipe 53, the port or passage 51, the annular groove45, the ports 48 (Figure 6), the left-hand end of the valve bore 12, theoutlet port 40 and the exhaust passageway 36 (Figure 3). The piston 120,piston rod 118 and Across head 105, together with the movable clampingdevice 103 then move to the right to their retracted positions shown inFigure 7, completing the cycle.

If at any time the pressure within the inlet port 20 rises to a pointwhere it overcomes the thrust of the relief valve spring 28, such aswhen the piston 120 reaches the end of its stroke, the relief valvepiston 24 is pushed to the right (Figures l and 3), opening the port 23between the inlet port or passage 20 and the forward end of the bore 22.The pressure lluid thus is tree to pass directly from the inlet port orpassage 20 through the port 23 into the port or passage 35 (Figures 3and 5), and thence through the exhaust passage 36 into the exhaust pipe38 and thence back to the reservoir.

What I claim is:

l. A hydraulic control valve unit comprising a casing having a valvebore and a pressure lluid inlet port and exhaust port, a pair of mainservice ports and an auxiliary service port communicating with saidvalve bore; a main valve member in said valve bore selectively movableinto a plurality of positions connecting said inlet port with one ofsaid main service ports while connecting said exhaust port with theother main service port; a blocking valve in one of said main serviceports selectively movable to open and close the same, a yieldableelement normally yieldingly urging said blocking valve into its serviceport closing position, said auxiliary service port being disposed infree communication with the space between said fluid inlet port and themain service port equipped with said blocking valve when said inlet portand said valve-equipped main service port are in communication with oneanother, said blocking valve having a valve operating chamber, anoperating piston therein movable in the opposite direction to thedirection of thrust of said yieldable element to overcome said thrustand shift said blocking valve into its open position in response to theattainment of a predetermined fluid pressure in said valve operatingchamber, and a constricted uid passageway connecting said valveoperating chamber to said inlet port to impede the flow of pressurefluid therethrough and delay opening of said blocking valve until afterpressure fluid has owed from said inlet port through said auxiliaryservice port.

2. A hydraulic control valve unit comprising a casing having a valvebore and a pressure uid inlet port and exhaust port, a pair of mainservice ports and an auxiliary service port communicating with saidvalve bore; a main valve member in said valve bore selectively movableinto a plurality of positions connecting said exhaust port with theother main service port; a blocking valve in one of said main serviceports selectively movable to open and close the same, a yieldableelement normally yieldingly urging said blocking valve into its serviceport closing position, said auxiliary service port being disposed infree communication with the space between said iluid inlet port and themain service port equipped with said blocking valve when said inlet portand said valve-equipped main service port are in communication with oneanother, said blocking valve having a valve operating chamber and avalve-operating piston therein movable in the opposite direction to thedirection of thrust of said yieldable element to overcome said thrustand shift said blocking valve into its open position in response to theattainment of a predetermined uid pressure in said valve operatingchamber, and a pair of constricted fluid passageways connecting saidoperating chamber to said valve-equipped main service port on oppositesides of said blocking valve to impede the ow of pressure luidtherethrough and delay opening of said blocking valve until afterpressure uid has ilowed from said inlet port through said auxiliaryservice port.

3. A hydraulic valve unit comprising a casing having a main valve bore,a pressure-fluid inlet port, an exhaust port, a pairof main serviceports and an auxiliary service port communicating with said valve bore;a main piston valve reciprocably mounted in said valve bore and havingheads selectively movable into a plurality of positions connecting saidinlet port with one of said main service ports while connecting saidexhaust port with the other main service port; a blocking valve disposedacross one of said main service ports and selectively movable to openand close the same, a yieldable element normally yieldingly urging saidblocking valve into its service port closing position, said auxiliaryservice port being disposed in free communication with the space betweensaid uid inlet port and the main service port equipped with saidblocking valve when said inlet port and said valveequipped main serviceport are in communication with one another, a blocking valve operatingchamber in said casing, a blocking valve operating piston reciprocablymounted in said operating chamber and connected to said blocking valve,said operating chamber having a passageway opening into saidvalve-equipped service port inwardly of said blocking valve, saidoperating piston being movable in the opposite direction to thedirection of thrust of said yieldable element to overcome said thrustand shift said blocking valve into its open position in response to theattainment of a predetermined uid pressure in said valve operatingchamber whereby to defer opening of said blocking valve until afterpressure fluid has owed from said inlet port through said auxiliaryservice port.

4. A hydraulic valve unit comprising a casing having a main valve bore,a pressure-fluid inlet port, an exhaust port, a pair of main serviceports and an auxiliary service port communicating with said valve bore;a main piston valve reciprocably mounted in said valve bore and havingheads selectively movable into a plurality of positions connecting saidinlet port with one of said main service ports while connecting saidexhaust port with the other main service port; a blocking valve boredisposed across one of said main service ports, a blocking valve membershiftably mounted in said blocking valve bore and 4selectively movableto open and close the same, a yieldable element normally yieldinglyurging said blocking valve into its service port closing position, saidauxiliary service port being disposed in free communication with thespace between said uid inlet port and the main service port equippedwith said blocking valve when said inlet port and said valve-equippedmain service port are in communication with one another, a blockingvalve operating chamber in said casing, a` blocking valve operatingpiston reciprocably mounted in said operating chamber and connected tosaid blocking valve, said operating chamber having a passageway openinginto said valveequipped service port inwardly of said blocking valve,said operating piston being movable in the opposite direction to thedirection of thrust of said yieldable element to overcome said thrustand shift said blocking valve into its open position in response to theattainment of a predetermined uid pressure in said valve operatingchamber to defer opening of said blocking valve until after pressurefluid has ilowed from said inlet port through said auxiliary serviceport.

5. A hydraulic valve unit comprising a casing havingy a main valve bore,a pressure-Huid inlet port, an exhaust port, a pair of main serviceports and an auxiliary service port communicating with said valve bore,a main piston valve reciprocably mounted in said valve bore and havingheads selectively movable into a plurality of positions connecting saidinlet port with one of said main service ports while connecting saidexhaust port with the other main service port; a blocking valve boredisposed across one of said main service ports, and a blocking valvemember reciprocably mounted in said blocking valve bore and selectivelymovable to open and close the same, a yieldable element normallyyieldingly urging said blocking valve into its service port closingposition, said auxiliary service port being disposed in freecommunication with the space between said fluid inlet port and the mainservice port equipped with said blocking valve when said inlet port andsaid valve-equipped main service port are in communication with oneanother, said blocking valve having a valve operating chamber, a valveoperating piston therein movable in the opposite direction to thedirection of thrust of said yieldable element to overcome said thrustand shift said blocking valve into its open position in response to theattainment of a predetermined tluid pressure in said valve operatingchamber, and a constricted fluid passageway connecting saidvalve-operating chamber to said inlet port to delay opening of saidblocking valve.

6. A hydraulicfvalve unit comprising a casing having a main valve bore,a pressure-iluid inlet port, an exhaust port, a pair of main serviceports and an auxiliary service port communicating with said valve bore,a main piston valve reciprocably mounted in said valve bore and havingheads selectively movable into a plurality of positions connecting saidinlet port with one of said main service ports while connecting saidexhaust port with the other main service port; a blocking valve boredisposed across one of said main service ports, a blocking valve memberreciprocably mounted in said blocking valve bore and selectively movableto open and close the same, a yieldable element normally yieldinglyurging said blocking valve into its service port closing position, saidauxiliary service port being disposed in free communication with thespace between said fluid inlet port and the main service port equippedwith said blocking valve when said inlet port and said valve-equippedmain service port are in communication with one another, said blockingvalve having a valve operating chamber, a valve operating piston thereinmovable in the opposite direction to the direction of thrust of saidyieldable element to overcome said thrust and shift said blocking valveinto its open position in response to the attainment of a predeterminedfluid pressure in said valve operating chamber, and a pair ofconstricted uid passageways connecting said valveoperating chamber tosaid valve-equipped main service port on opposite sides of said,blocking valve to delay opening of said blocking valve.

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